The purpose of this project is to provide consultative services in statistical and epidemiological methodology in the design, interpretation, and evaluation of clinical trials of diagnosis and treatment of cancer and other studies requiring this kind of expertise. For some trials the Section provides full statistical support including development of detailed study plans, assistance in the design of appropriate study forms, supervision of randomization and collection, processing, and editing of data, performance of interim analyses during the progress of the study, preparation of progress reports, final analysis of study data, and collaboration in the preparation of scientific papers. During the last year the Section has provided such full statistical support for several large-scale, multicenter, randomized clinical trials of cancer treatment. At present there is one active protocol for testis cancer, two for brain tumors, and six for lung cancer. In the area of diagnosis, important work includes the evaluation of multiple serum markers in lung cancer, and evaluation of the Makari skin test as a diagnostic test for colorectal, lung, and breast cancer. In another project a large data bank is maintained with information on patients with breast cancer, most of whom have had estrogen receptor measurements performed at least once. In collaboration with the Markers Group of the Breast Cancer Task Force, the Section is responsible for an inventory and information file containing data on over 10,000 women for whom serum samples are available for evaluating serum markers for breast cancer. Additional consultative activity involves collaboration with other scientists in projects such as a study of the geographical variation in death rates from lung cancer in the U.S., and investigation of personality factors in fibrocystic and malignant breast disease, and analyses of prognostic factors and practical staging systems for mycosis fungoides.